1. Field of the Invention
The invention relates to test systems and more specifically to a programmable test point selector circuit which permit the pins of the connector used to interface a general purpose test set with the system to be tested to be programmed as either multivoltage stimuli (input) or multivoltage measurement (output) points.
2. Description of the Prior Art:
Typical prior art general purpose test sets provide a predetermined number of pins which were permanently designated for signal inputs (stimuli points) and another number of pins that were permanently allocated to outputs (measurement points). In utilizing these systems, adapters were built to interface the test set with the system to be tested. The disadvantages of this arrangement were that there was no capability of redistributing the available pins between inputs and outputs, and each specific system to be tested required its own specially designed interface adapter to mate the test set with the system being tested. These test sets normally applied and measured only one level of signal voltage. If some pins designated as inputs required different voltage levels or if the voltage appearing on any pin designated as an output required a different threshold value, special circuitry was normally designed into the unique adapter and the problem resolved in this manner rather than in the test set.
Other prior art test systems utilized relay networks to couple input signals to terminals designated by a program as inputs and to couple the terminals designated by a program as outputs to the test set. These systems tend to be slow due to the operating times of the relays and also have the reliability and electrical noise problems inherent in electromechanical components. Additionally, these systems did not provide means for selecting mixed multivoltage levels to be used as input signals or means for programming the threshold for pins designated as outputs.